The present invention relates to an apparatus and method for detecting a presence or position of a substrate on a support.
In the fabrication of integrated circuits, flat panels, and electrical circuits, electronic devices are formed by depositing and etching layers on a substrate. In these processes, the substrate is transferred by a robot from a substrate holder to a support in a chamber. The robot extends a blade into a slot of the substrate holder, lifts up the substrate, moves the substrate to a support in the chamber, and lowers the substrate onto lift pins that extend through the support. The lift pins descend to place the substrate on the support. Thereafter, process gas is provided in the chamber and energized by RF or microwave energy to process the substrate.
In these methods, it is desirable to detect the presence and position of the substrate on the support because a misplaced substrate can lead to inferior processing of, or damage to, the substrate. Such improper positioning can occur when the substrate is displaced in its slot in the substrate holder and is picked up a skewed position by the blade. The substrate can also shift position on the blade during transportation. In addition, the substrate can move while resting on the descending lift pins due to ambient vibrations. Such improper positioning is often not discovered until the substrate is fully processed and is already damaged. For example, in photolithography, the substrate has to be precisely oriented; otherwise, the pattern of light projected onto the substrate is distorted or skewed. A misplaced substrate can also result in disparate heat transfer rates across the backside of the substrate which result in non-uniform processing rates across the front face of the substrate. Also, heat transfer gas held below the substrate can leak out at inconsistent rates from below the edge of the substrate if the seal with the overlying substrate is not uniformly gas tight across the backside of the substrate.
Thus there is a need for an apparatus and method to determine a presence of a substrate on a support. It is also desirable to detect proper positioning of the substrate prior to clamping down or otherwise initiating processing of the substrate to avoid damaging the substrate. It is further desirable to securely hold the substrate after it is properly positioned.
An apparatus and method according to the principles of the present invention are capable of, detecting a presence of the substrate, and optionally, determining whether a substrate is properly positioned on a support. The apparatus comprises a support adapted to support the substrate, the support comprising a window. A radiation source is adapted to direct radiation through the window in the support. A radiation sensor is provided in a path of the radiation, the radiation sensor adapted to detect a presence of the substrate on the support by measuring a property of the radiation.
In another aspect, the present invention comprises a chamber for processing a substrate, the chamber comprising a gas distributor having a nozzle adapted to introduce process gas into the chamber. An electrostatic chuck in the chamber comprises a surface adapted to receive the substrate, and a window adapted to transmit radiation therethrough. A radiation source is adapted to pass radiation through the window of the electrostatic chuck. A radiation sensor in a path of the radiation is adapted to detect the substrate on the surface of the electrostatic chuck by measuring a property of the radiation.
In yet another aspect, the present invention comprises a chamber for processing a substrate, the chamber comprising a gas distributor having a nozzle adapted to introduce process gas in the chamber; a support having a surface adapted to receive the substrate; and means for sensing a presence of the substrate on the support by detecting a radiation passing through the support.
In yet another aspect, the present invention comprises an electrostatic chuck for holding a substrate. The electrostatic chuck comprises a dielectric having a surface adapted to receive a substrate, the dielectric covering an electrode that is chargeable to electrostatically hold the substrate, and the dielectric comprising a window.
In another aspect, the present invention comprises a method for detecting a presence of a substrate on a support in a chamber, the method comprising the steps of placing the substrate on the support, passing radiation through the support, detecting the radiation to determine a presence of the substrate on the support.
In another aspect, the present invention comprises a method of detecting a presence of a substrate on a support in a chamber, the method comprising steps of placing the substrate on a support in the chamber; passing a light beam through a window in the support; and detecting the light beam transmitted through the window to detect a presence of the substrate on the support.